BAGHDAD, Sept. 29 — American officials have warned Iraqi leaders that they might have to curtail aid to the Interior Ministry police because of a United States law that prohibits the financing of foreign security forces that commit “gross violations of human rights” and are not brought to justice.

The Interior Ministry, dominated by Shiites, has long been accused by Sunni Arabs of complicity in torture and killings.

The American ambassador to Iraq, Zalmay Khalilzad, said in an interview on Friday that “at this point” Iraq had not been formally notified that its national police were in violation of the legislation, known as the Leahy Law. He said he remained optimistic that Iraqi officials would “do the right thing” and resolve the matter. Nonetheless, he said American officials had begun reviewing programs that might have to be ended.

The issue centers on one of the most sensitive subjects within the Iraqi government: the joint Iraqi-American inspection in May and subsequent investigation of a prison in eastern Baghdad known as Site 4.

Within the prison there was clear evidence of systematic abuse and torture, including victims who had “lesions resulting from torture” as well as “equipment used for this purpose,” according to a human rights report later published by the United Nations mission in Iraq.

The prison, run by an Interior Ministry national police unit, had more than 1,400 prisoners crowded into a small area. An American officer said some had been beaten or bound and hung by their arms. At least 37 teenagers or children were in the prison.